International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org, editorijaiem@gmail.com
Volume 2, Issue 8, August 2013
ISSN 2319 - 4847
Design and Fabrication of Eccentric Turning
Attachment
Dr G. Naga Malleshwar Rao1, Dr S.L.V.Prasad2, P. Sreenivasulu3
1,2
Professor of Mechanical Engg., SSSISE, Ananatapuram, AP.,India.
Associate Professor in Mechanical Engg., SSSISE, Ananatapuram, AP.,India
3
ABSTRACT
Man always put his efforts to save his energy and the time required to do his work. At the same he is also worried about the
quality of the products he produced and cost of the product. It is felt that during eccentric turning quite a good amount of time is
spent in setting up the job in a four jaw chuck. Moreover even for a skilled turner it is a laborious and tedious to set the job for
eccentric in a four jaw chuck. The present work is aimed at reducing the setup time for eccentric turning in a four jaw chuck by
designing and fabricating an eccentric turning attachment. This designed attachment consists of simple parts such as V-block,
studs, center plate, center rod, base plate, nuts, scale etc,. The fabricated eccentric turning attachment is tested experimentally
and the desired results have been obtained. The set-up time can be reduced drastically by using this attachment.
Key words: Eccentric Turning, four jaw chuck, skilled turner, Set-up time.
1. INTRODUCTION
The lathe is one of the oldest machine tools and came into existence from the early tree lathe which was then a device for
rotating and machining a piece of work held between two adjacent trees. A rope wound round the work with its one end
being pulled by a man caused the job to rotate intermittently with its further development a strip of wood called “lath”
was used to support the rope and that is how the machine came to be known as “lathe”. This device continued to develop
through centuries and in the year 1797, HENRY MAUDSLAY an Englishman, designed the first screw cutting lathe
which is the forerunner of the present day high speed heavy duty production lathe, a machine tool which has practically
given shape to the present day civilization by building machines and industries. [1]
2. ECCENTRIC TURNING
2.1. Definition
A disc or wheel having its axis of revolution displaced from its center, so that it is capable of imparting eccentric motion.
It can be defined in the other way as, if a cylindrical work piece has two separate axis of rotation, one being out of center
at the other, the work piece is termed as eccentric and turning of different surfaces of the work piece is known as
“Eccentric Turning”.
2.2. Importance of eccentric turning
Eccentric turning has the following applications:
1. In Automobile engineering:
a. For crankshaft turning.
b. For turning eccentric rods for opening and closing of inlet and exhaust valves.
2. In Marine steam engines:
For the movement of valve gears and reversing valve gears.
Each valve is moved up and down by eccentric and eccentric rod. Each eccentric is a circular disc mounted on the
crankshafts, but mounted off-center.
Therefore as the crankshaft rotates the eccentric moves up and down. Because each eccentric circular it can turn within
the strap that surrounds it, thus pushing and pulling the eccentric rod up and down as the crankshafts turns. This up
and down motion of the eccentric rod, which works like a connecting rod, is passed to the valve rod to drive the valve up
and down.
1. In aircrafts:
2. For aircraft bushings.
3. Self-lubricating bushings.
4. Corrosion resistance bushings.
5. Alloy bushings.
6. Metric bushings.
7. Stainless steel bushings.
Volume 2, Issue 8, August 2013
Page 199
International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org, editorijaiem@gmail.com
Volume 2, Issue 8, August 2013
ISSN 2319 - 4847
8. Poly, Urethane bushings.
9. Precision bushings.
10. In water treatment:
Eccentric plug valves are sometimes also called globe valves .The eccentricity of plug allows to seal against the seating
without sliding contact, so that all metal trim can be used. With all metal parts in contact, eccentric plug valves are
suitable for more severe, high temperature, high pressure control applications.
5. It is used in power press, guillotine machine and press breaks. It is also used in automatic control.
6. As control shafts (engaging a back gear on a lathe with stepped pulley drive), for fixing purposes, presses etc.[2]-[4]
2.3. Hindrances of Eccentric Turning In Usual Method
1. It is very laborious process.
2. Time consuming process, hence low productivity.
3. Only skilled operator can set the job easily.
4. Accuracy is less.[5]-[6]
3. ECCENTRIC TURNING ATTACHMENT (ETA)
3.1. Need for an Eccentric Turning Attachment
Eccentric turning is one, which is a difficult and time-consuming operation. In fact there are various methods of eccentric
turning out of which eccentric turning by fixing a job in four-jaw chuck is tedious and time consuming operation.
For certain mass production activities such as, production of crank shafts, eccentric of I.C. engines there are specialized
machine tools where production can be carried out at fast rate without any difficulty. But when the job work is to be done
according to consumer’s requirement inevitable one has to go to produce the required eccentric with the help of four jaw
chuck only. It becomes still more difficult when job is of irregular in nature.
Hence it is decided to design a simple, and easy to operate, “Eccentric Turning Attachment (ETA)” which will reduce
tediousness and burden on the operator to fix a job for eccentric turning in a four jaw chuck.
3.2. Description of the attachment
Attachment consists of a V-block, studs, center plate, center rod, base plate, nuts, scale etc,. The detailed construction of
eccentric turning attachment are shown in the figures----
Figure 1 Pictorial view of Eccentric Turning Attachment
Figure 2 Assembled Diagram of Eccentric Turning Attachment
Volume 2, Issue 8, August 2013
Page 200
International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org, editorijaiem@gmail.com
Volume 2, Issue 8, August 2013
ISSN 2319 - 4847
3.3. Procedure for eccentric turning on lathe using ETA
STEP 1: Marking is to be done on the work piece as per the requirements with help of scriber, angle plate, v-block,
surface plate and a dot punch.
Figure 3 Application of ETA
STEP 2: After marking is done, the work is placed on the v-block of ETA. The eccentric center of the work piece is
adjusted to the height of the dead center by adjusting the nuts of ETA.
STEP 3: Once the eccentric is aligned with the tailstock center, the attachment will be moved towards the 4-jaw chuck
and work piece will be firmly fixed.
4. PRACTICAL APPLICATION OF THE FABRICATED ETA
The following two jobs namely job1 and job 2 are turned eccentrically by using ETA and time taken to set the job is
measured and compared for both methods by using stop watch. The details of the time taken and others are given in the
tables 1 & 2 respectively.
Figure 4 Job1
Figure 5 Job2
Table.1: Set-up time for Job 1
S. No
Setup time in usual
method (in min)
1.
Setup time using
ETA (in min)
3’49’’42
Difference in min
1’01”73
2’48’’09
From the above table it is evident that, for job1 82.3% of time is saved by using ETA.
Table.2: Set-up time for Job 2
S. No
Setup time in usual method (in min)
1.
Skilled
Operator
15’23’’03
2
13’15’’56
Setup Time using ETA(in
min)
Diameter of work piece
(In mm)
Semi-skilled Operator
Volume 2, Issue 8, August 2013
25’10’’45
5’24’’47
20
23’13’’02
3’03’’48
15
Page 201
International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org, editorijaiem@gmail.com
Volume 2, Issue 8, August 2013
ISSN 2319 - 4847
In job2 for skilled operator 70.85% of time can be saved and for semi skilled labor 82.77% of time is saved to set the job
for eccentric turning by using ETA.
5. SALIENT FEATURES OF THE ECCENTRIC TURNING ATTACHMENT








The attachment is more economical.
The attachment is simple in construction.
Semi skilled operator can also set the job efficiently and perform the work.
The attachment is compact and gives better appearance.
It requires no external power source for movement.
Setting time is drastically reduced when compared with usual methods and hence productivity is highly increased.
No expensive material is necessary to construct the attachment.
No special manufacturing methods are necessary to manufacture the attachment.
6. CONCLUSIONS
The basic task in designing an eccentric turning attachment is to reduce the setup time and the same is proved successfully by
fabricating and testing the attachment by turning two models.
The important benefits that can accrue out of using the eccentric turning attachment as compared to the usual methods are:
 Drastic reduction in setup time, the time taken to set the job for model 1 is reduced from 3’49’’42 to 1’01’’73 that is 82.3%
reduction is achieved. For job 2, it is 70.85% for skilled operator and 82.77% reduction in setup time for semiskilled
operator is achieved.
 Less skilled operators can also turn eccentrics efficiently by setting the job quickly and easily with the help of eccentric
turning attachment.
 Simplified design and construction, of eccentric turning attachment do not arise any external power source to operate it
when compared with other lathe attachments.
 Eccentric turning attachment is inexpensive, as no special manufacturing methods are needed to manufacture it.
 The general materials such as low carbon steels (mild steel) are used to make the attachments, thus the material used also
inexpensive. This eccentric turning attachment costs very low when compared to other attachments. If this attachment is
manufactured in bulk the cost can be four times reduced. The attachment is highly useful for job working shops.
 Productivity in industries can be accelerated to the maximum extent with the help of eccentric turning attachment.
 Accuracy of the turned eccentrics can be highly increased.
 More flexibility makes the attachment for simple and easy maintenance.
 This design is a tentative one and need some more modifications, for example v-block movement in longitudinal and in
cross directions and center rod can be lowered or raised instead of studs.
 Limitations: The attachment is helpful in eccentric turning of jobs of 75 mm diameter and 150 mm length. For heavy jobs,
the attachment will become lighter hence they have to go to eccentric turning lathe.
If these attachments are produced on mass scale, by machine tool manufacturers and supply with the lathe that will be highly
useful to the user in maintaining the quality at an optimal cost. With all hopes of bringing it as a useful attachment, the lathe
attachment is fabricated as a research work.
References
[1] Hajra Choudary.S.K., S.K. Bose, A.K. Hajra Chowdhary “Elements of workshop Technology vol: II” Machine toolsMedia promoters and publishers Pvt, 1984, (pp: 78-133).
[2] Heinrich Gerling –“All about machine tools”- Wiley Eastern private limited New Delhi 1974, (pp: 64-66).
[3] W.A.J. Chapman-“Work shop Technology: part 2” –Viva books private limited, 1972, (pp: 127-128).
[4] C.Elanchezhian, M.Vijayan- “Machine tools”- Anuradha agencies publishers, 2004, (pp: 1.59-1.60).
[5] T.K.Kundra,P.N. RAO, N.K Tewari- “Numerical Control and Computer Aided Manufacturing” –Tata Mc Graw
Hill Publishing Company Limited 2002, (pp: 73-81).
[6] Dr. P. Radha Krishnan, “Manufacturing Technology vol-1”- Scitech Publications (India) Private Limited 2002, (pp:
258).
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